Groups of pregnant rats will be subjected to both acute-high dose exposures and chronic-low dose exposures of anesthetic gases to study the possible embryolethal and/or teratogenetic effects of such exposures in rats. Acute high dose experiments will subject groups of rats to 4-hour anesthetic exposures. Separate groups will be exposed day 8, 9, 10, 11, 12, 13, 14, and 15 of the pregnancy. Chronic low dose experiments will subject groups of rats to 8-hour daytime, 8-hour nighttime., or 24 hour/day anesthetic exposures daily from days 8-15 of the pregnancy. Animals will be sacrificed and examined on day 20 of the 21 day pregnancy. Data subjected to statistical analysis will include the incidence of 1) abnormal litters, 2) abnormal fetuses/litter, 3) specific cogenital anomalies, and 4) fetal mortality. The chronic exposure studies will also be analyzed to determine whether differences exist with 8 hour vs. 24 hour exposure, and whether a diurnal variation in the effects exists. BIBLIOGRAPHIC REFERENCE: Corbett, TH, Beaudoin, AR, Cornell, RG, et al.: Toxicity of Polybrominated Biphenyls (Firemaster BP-6) in Rodents. Environmental Research 10:390-396, 1975.